In known splicing devices for joining together two thread ends, a turbulence chamber is provided, the chamber normally being constructed as a cylindrical channel. The two oppositely directed thread ends to be joined together are inserted in the channel. In the axial center of the turbulence chamber is placed a compressed air passage having an opening which is tangential to the peripheral wall of the turbulence chamber and through which compressed air is blown into the chamber so that the two thread ends are jointly subjected to turbulence and are joined. In the known devices, a disadvantage exists that, although the tangentially entering air leads to good turbulence effect on the fibers of the thread ends, an angular momentum is produced, increasing the twist of the thread ends at one side of the turbulence chamber and decreasing or even eliminating the twist on the other side thereof. Overtwisting the thread end at one side can damage individual fibers, whereas on the other side a weak point with reduced tensile strength is formed due to the lack of a reciprocal hold in the region of reduced or non-existant twist. An example of this is shown in German Offenlegungsschrift No. 28 56 514.
This method has the further disadvantage that, on one side of the splicing point, the twisting direction of the spliced joint coincides with the prior twist of the thread, whereas on the other side of the splicing point the twisting direction is opposite to that of the twisting direction of the thread. Therefore, different turbulence chambers are required for S- and Z-yarns in order to be sure that, during further processing, the end with the coinciding twisting direction of the splicing joint always passes through before the other end with the non-coinciding twisting direction. In addition, any remanent bobbins must be re-wound twice to fulfill the aforementioned condition. However, this involves additional stressing and higher processing costs in connection with the thread.
In another known splicing apparatus, shown in German Offenlegungsschrift No. 28 15 999, the turbulence chamber has a trapezoidal cross-section in which the larger trapezoidal side is formed by a cover which can be pivoted for opening and closing the turbulence chamber. As in other known turbulence chambers, the compressed air is injected into the center of the chamber through openings located on the smaller trapezoidal side of the chamber cross-section facing the cover. This arrangement produces air eddy currents in the turbulence chamber which are undefined to a greater or lesser extent, so that there is also undefined mixing of the fibers.